1. Field of the Invention
The present invention relates generally to measuring rules and more particularly, to vertically extensible story poles and elevational grade rods.
2. Brief Description of the Prior Art
There are in the prior art a variety of vertical measuring devices. One such device is shown in U.S. Pat. No. 1,614,577 to Tetrick. Tetrick apparently teaches an expansion story-pole which can be used for measuring height, leveling, plumbing and spacing. The Tetrick device does not teach story pole which is direct read. Some calculation is needed in order to determine the vertical-height measure. It is also noted that the Tetrick device cannot be used as a direct read elevation rod.
Another extensible measuring device is depicted in U.S. Pat. No. 3,094,787 to Moore. The Moore rule does not provide direct read capabilities and further, it cannot be used as a direct read horizontal grade rod. Moore merely teaches a telescoping measuring rule comprised of a plurality of angle sections.
U.S. Pat. No. 4,099,331 to Peterson et al. is directed to another extensible measuring device. The Peterson et al device incorporates a vertically extendable slide which engages a wheel which is rotated in response to the movement of the vertical slide. The wheel acts as a counter to measure the distance which the vertical slide is extended. Such distance must be read and then added to the length of the tool. Therefore, Peterson et al does not provide a direct read story pole. Further, the Peterson et al device cannot be used as a direct read horizontal grade rod.
Another telescoping measuring rule is taught in U.S. Pat. No. 4,399,616 to Jansson. The Jansson device containes two scales, one for taking outside measurements and one for taking inside measurements. Apparently, the Jansson rule can be used to take a direct reading when utilizing the inside measurement scale. However, there is no way that the Jansson rule can be used as direct read horizontal grade rod.